Preparation of esters



Patented Jan. 14, 1941 UNITED STATES PREPARATION OF ESTERS Anthony H.Gleason, Elizabeth, N. J assig'nor to Standard Oil Development Company,a corporation of Delaware No Drawing. Application April 1, 1937,

Serial No. 134,304

11 Claims.

This invention relates to the preparation of esters and it relates moreparticularly to the preparation of products of the type of acetoaceticesters by reaction of polymers of ketenes,

especially cyclobutane 1:3 dione which is the dimer of ordinary ketene,with monohydroxy alcohols.

This application is a continuation-in-part of copending application ofPeter J. Wiezevich and Anthony H. Gleason, Serial No. 720,946, filedApril 17, 1934, now Patent No. 2,103,505, which in turn is acontinuation-in-part of the Wiezevich and Gleason application Serial No.559,936, filed August 28, 1931, now Patent 1,998,404.

In Patent 1,998,404,.a method was described for the preparation in highyieldsof cyclobutane 1:3 dione presumably having the formula O:C-CH2H2CC=O by the polymerization of ketene (Cl-I2:CO) by contacting it witha metallic surface promoting the polymerization of the ketene.

The cyclobutane 1:3 dione (B. Pt. about 127 5 0.) so prepared may beconsidered as the anhYdmfl aceto-acetic acid since it reacts with waterto gi e aceto-acetic acid and. under suitable conditio 5 may be made toreact with various other compounds. Thus, although the 3 diketene is blieved to have the cyclic structure illustrated a ove, yet in certainrespects it acts the formula CH3.CO.CH:CO. The anism of the reaction orreactions inolved in the conversion of the diketene (cyclob utane 1:3dione), which has a cyclic structure, into linear type compounds, suchas aceto-acetic acid or esters thereof, is not well understood, althoughit is believed that the cyclic compound is unstable and that in somemanner the ring structure breaks and opens up into a linear typecompound. It is also unstable in that frequently simple acetates areformed (from the group CH3.CO) instead of aceto-acetates.

The present invention deals with treating this dim-er, as well as anyother polymerization products of ketene, such as dehydroacetic acidhaving the formula CH CO.CHCOOC(CH ):CHCO

50 or other higher polymers, under suitable conditions, with monohydroxyalcohols to produce esters. For instance, ethyl alcohol when reactedwith diketene forms ethyl aceto-acetate. Other saturated aliphaticmonohydroxy alcohols may .55 be used such as methyl, isopropyl, octyl,lauryl,

and octadecyl alcohols. Other alcohols which may be used includeunsaturated alcohols such as butenyl and oleyl alcohols, aromaticderivatives of aliphatic alcohols, for instance, benzyl alcohol, phenylethyl alcohol, etc., and also alcohols having a saturated ring structuresuch as cyclohexanol and naphthenic alcohols.

According to the present invention, it has been discovered that in spiteof the thermal instability of the diketene, high yields of the desiredacetoacetic esters are obtained by carrying out the esteriflcation atslightly elevated temperatures, such as from about 50 C. up to theboiling point of the diketene (127 0.), although the temperature ispreferably maintained between the approximate limits of 80 and 100 C.When lowboiling alcohols are used, the reaction is preferably carriedout under reflux.

Some other preferred reaction conditions are mentioned briefly herewith.The proportions of reactants should be maintained between theapproximate limits of 0.5 and 5 mols of the alcohol to 1 mol of theketene polymer. With the lower molecular weight alcohols, the proportionshould preferably be between about 1 and. 2 mols of the alcohol to 1 molof the ketene polymer, whereas with higher boiling alcohols a ratio of1:1 is preferably maintained or a slight excess (e. g. 5 or 10%) of thealcohol. The reaction time will, of course, depend to some extent uponthe temperature and the concentration of reactants and will normally beabout 2 to 3 hours for a temperature of about 80 to 100 C. The reactionshould be carried out in the presence of a small amount ofesterification catalyst which is preferably an acid such as hydrochloricacid, sulfuric acid, phosphoric acid or (11- or trichloracetic acid, theamount to be used ranging from about 0.5 to 3%, or preferably about 1 to2%, by weight of the total reactants. The reaction is also preferablycarried out in the presence of a diluent or solvent such as benzene,toluene, ethylene dichloride, trior tetrachlorethane, etc., especiallywhen the ketene polymer is reacted with a higher alcohol. (When loweralcohols are used an excess of the alcohol may serve as diluent.) It isbelieved that this diluent assists in controlling the reaction in favorof the desired esterification rather than permitting undesirabledecomposition or side reactions to take place, such as the breaking upof the acetoacetic esters to form simple acetates.

In carrying out the invention, the alcohol and the ketene polymer may bemixed in a suitable container and. then the catalyst added. Finally,

the entire mixture is heated for the required reaction time. If desired,this order of procedure may be varied to some extent as will beunderstood by those skilled in the art.

Although the invention has been particularly described with reference toand is preferably carried out with diketene or other polymers of aceticketene, polymers of other ketenes, such as methyl ketene CHsCI-ICO,etc., may be used. The following example is given for the sake ofillustration and without intention of limiting the invention to thespecific details disclosed:

Example When diketene was treated with an excess of alcohol and a traceof sulfuric acid, only traces of ester could be found and at the end of10 days the odor of the dimer from the reaction mixture was stillpronounced, thus indicating that only little, if any, esterification hadtaken place.

Another sample of the diketene (37 g.) was heated under reflux on asteam bath (100 C.) with 40 g. of absolute ethyl alcohol and 0.3 g. ofsulfuric acid for 3 hours. In spite of the thermal instability of thepolymer, a yield of 80-85% of ethyl aceto-acetate, boiling at 68 C. at10 mm. pressure was obtained by washing the reaction product withsaturated salt solution, drying, filtering, and distilling under vacuum.

The foregoing description is merely illustrative and it is not intendedthat the invention be limited by any of the theories suggested as to theoperation of the invention.

I claim:

1. The method of preparing aceto-acetic esters which comprises reactinga polymer of ketene with a monohydroxy alcohol at a temperature above C.in the presence of a small amount of an acid serving as esterificationcatalyst.

2. The method of preparing aceto-acetic esters which comprises reactingabout 0.5 to about 5.0 mols of a monohydroxy alcohol with 1 mol ofdiketene at a temperature above 50 C. in the presence of a small amountof an acid serving as esterification catalyst.

3. Method according to claim 2 in which lower aliphatic alcohols areused.

4. The method of preparing ethyl acetoacetate which comprises heatingdiketene with an excess of ethyl alcohol to a temperature of about toabout C. in the presence of a small amount of sulfuric acid.

5. Method according to claim 4 in which approximately 2 mols of ethylalcohol are used for each mol of diketene, and the reaction is carried 1out in the presence of about 1 to about 2% of sulfuric acid based on thetotal weight of diketene and alcohol.

6. In the process of preparing esters by the reaction of a ketenepolymer with a monohydroxy alcohol in the presence of an esterificationcatalyst, the step of heating the reaction mixture toa temperature above50 C., but not above the boiling point of the ketene polymer.

7. The process according to claim 6 carried out in the presence of adiluent.

8. The method of preparing ethyl aceto-acetate which comprises heatingone molecular proportion of diketene with substantially two molecularproportions of ethyl alcohol at a temperature of about 100 C. in thepresence of substantially 0.006 molecular proportions of sulfuric acid.

9. The method of preparing ethyl aceto-acetate which comprises heatingone molecular proportion of diketene with substantially two molecularproportions of ethyl alcohol at a temperature of about 100 C. in thepresence of substantially 0.006 molecular proportions of sulfuric acidfor a period of about three hours.

10. The method of preparing aceto-acetic esters which comprises reactinga polymer of ketene with a monohydroxy alcohol at a temperature of about80 to about 100 C. in the presence of a small amount of an acid servingas esterification catalyst.

11. The process of preparing aceto-acetic acid esters which comprisesreacting diketene with an aliphatic monohydroxy alcohol at a temperaturein excess of 50 C., in the presence of an acid esterification catalystand a liquid diluent.

ANTHONY H. GLEASON.

